The long term objective of Project V is to understand the biochemical events which direct the synthesis and deposition of myelin membranes in the CNS. Our basic hypothesis is that specific cell surface proteins are present on axonal membranes that participate in oligodendrocyte recognition, regulated membrane synthesis and the ordered wrapping and compaction of myelin membranes. We propose three different approaches toward identifying these proteins and elucidating their functional properties. The first approach is an extension of our previous studies which indicate that a specific oligodendrocyte adhesion receptor, a member of the integrin receptor family, may participate in the regulation of myelin gene expression. We plan to purify this receptor and clone the cDNA which encodes it. Antibodies against the receptor will be used to probe it's role in oligodendrocyte adhesion and myelin synthesis. The second section of this proposal is also directed at oligodendrocyte adhesion but here the emphasis is on the extracellular matrix component (ECM), produced by glial cells, which is recognized by oligodendrocytes in vitro. We plan to purify and characterize this component and determine if it is a previously recognized ECM protein. Antibodies directed against this protein will be used to determine its pattern of expression in developing brain. Our third plan of research includes two direct approaches toward the identification and purification of the axonal proteins which we propose to be involved in the process of myelin membrane wrapping. An in vitro myelination system will be used to screen a battery of anti-axonal membrane monoclonal antibodies for their ability to cause a specific disruption of oligodendrocyte-axon interactions and thus allow us to identify functional components of the machinery responsible for myelinogenesis. In addition to this immunological approach, we will carry out a more traditional biochemical search utilizing a bioassay for purification of these important axolemmal constituents.